The present invention relates to an outboard motor having an improved structure for assembling the same.
The major portion of an outboard motor is arranged in such a manner that an engine is mounted on an upper portion of an engine holder formed so as to provide substantially a horizontal plate-like shape which is connected to a hull, to which an outboard motor is mounted through a crank bracket. Generally, the engine is mounted on the engine holder in a standing fashion so that the crank shaft has a vertically attitude. In a case of a four-stroke-cycle engine, an oil pan is disposed below the engine holder to cause oil accumulated in the oil pan to be supplied to the inside portion of the engine to lubricate the inside of the engine.
The engine is composed by combining a crank case, a cylinder block, a cylinder head and the like. Hitherto, only the crank case and the cylinder block are secured to the engine holder, while the cylinder head is floated from the engine holder. Moreover, the engine and the oil pan are secured to the engine holder with individual fixing bolts.
However, in the above-mentioned layout, since only the crank case and the cylinder block of the engine are secured to the engine holder, the engine and the engine holder are connected to each other in a small area. Thus, there is apprehension that the rigidity of the mounted engine is insufficient in a case of a large size engine or the like.
Furthermore, since the cylinder head floats from the engine holder, it is impossible to directly return an oil in the cylinder head to the oil pan, it is necessary to adopt a structure that a specific oil returning passage is formed in the cylinder block to temporarily introduce oil in the cylinder head to the cylinder block and then return the oil to the oil pan. When the above-mentioned oil returning passage is formed, the structure of the cylinder block becomes too complicated to be easily manufactured and to reduce the weight.
Furthermore, since the engine and the oil pan are secured to the engine holder through individual fixing bolts, the rigidity of the overall assembled body of the outboard motor is unsatisfactory and reduction in the number of elements and assembling steps cannot be realized.